Full details on my forum. Here are the highlights:

1) Contrary to Sisk's experience, my mega-spikes did not go away as the barrel was shortened. Instead, the spikes moved closer to the breech. We don't know what that means yet, but it is an awesome clue.

2) Even though this OEM Remington barrel has 2000 - 3000 mega-spike rounds through it, there is absolutely no damage to the barrel, as confirmed by measuring the groove diameter of the cut-off pieces with a tri-mic. Bear in mind that Remington barrels are rumored to be heat treated and may have a yield strength of well over 100,000 psi. Other barrels may not be as strong (if anyone has access to a Rockwell hardness tester and would like to test one of my cut-offs, please contact me).

3) WW748 and WW760 have mere baby spikes with full throttle cast bullet loads. All other powders tried to date -- 3031, 4895, Big Game, and 4350 -- have mega spikes with cast bullets, though little or no spike with jacketed bullets. The Winchester powder is another awesome clue, though I am not sure what it means. One poster thinks that the WW powder may have a de-gressive burn rate, burning faster toward the muzzle.

4) The spike is NOT caused by ionized powder gases creating electrical noise as Oehler claims. I proved this by taping, not gluing, a strain gage onto the barrel next to my regular gages. The taped-on gage cannot read strain but is still susceptible to electrical noises. The taped-on gage would not even trigger the Pressure Trace.

Poppenman, do you notice differences in velocity between those rounds that have a secondary spike and those that don't? Also, do you note changes in the brass cases between those rounds generating secondary spikes and those that don't? I note above that you report absolutely no damage to your barrel, though ~3000 secondary MEGA spikes have occurred in it, some over 107,000 psi.

Acklely Improved, there is no simple way to compare velocity to spike vs. no spike because there is no simple way to turn the spike on and off. Full throttle cast bullets always have a mega-spike except with WW748 & 760. Barnes X bullets never have a mega spike. My 165 jacketed loads usually have a mini-spike that once in a great while becomes a midi-spike, and no, it doesn't seem to correlate to velocity variations.

In the seven odd years that I have been reloading for this rifle, only one case has failed (not counting neck splits) because of 75 KSI primary pressure thanks to a Quickload mis-prediction, as reported here about 6 weeks ago. I don't keep records on my cases, but some of them are as old as the rifle and may have been reloaded 25 - 40 times because I do a lot of load tinkering, and other than the one failure and the occasional split neck, the cases keep on trucking. Of course, the case that blew up Charlie's barrels never failed, either.

I don't claim to understand it. The more I learn, the more puzzled I become.

I am the one who mentioned that DB Ball is degressive after the progressive deterrent
burned off the outside, so when his slippery
bullets jump a little too fast, after they decide to move, and burning wants
to slow the inner part of the ball powder is in the open and is picking up burning speed so
fire isn't going out and having to catch up again.

On the W-760 data I asked on his forum if there was room for a little more powder, like 2 gr.
I also will ask that he try RE-15 and RE-19.
I asked if Sisk used cast bullets or light bullets like Denton.And Denton using light bullets should do hacksaw bit on a 7.62 that we can find him,sometime, to see if spikes go away in light of the fact that they didn't go away on Mtngun's heavier cast bullet loads.Need to find out how the two different ways that
spikes are made, are similiar and different.Ed.

Poppenman, if your cases show no signs of pressure and there are no velocity increases when the MEGA spikes occur, then how can the spikes be measuring true internal pressure? If the the pressure was reaching those MEGA heights, then the cases and the velocity should show the results. Thus, the spikes MUST represent some electronic glitch or a peculiar harmonic barrel/chamber phenomenon, which was described in the other thread.

I posted this on his site about his W-760
results which were better, like the 748 in
reducing spikes------

""I think I found the light....I think that 748 and 760 should have the peak pressure occurring
at about .65 to .90 M-sec like on jacketed bullet curves I have seen pictured elsewhere, not the .50
m-sec that stick powders usually do.

Ok that means your real tight cast bullet(which it has to be for accuracy),
temporarily starts a little hard, causing earlier than normal pressure peak timewise, then slippery bullet having been engraved jumps ahead much faster than same wt jacketed.
Burn slows then picks back up
so that there is even a real small bump from 760 and 748.You look at 760 trace and if peak was moved say to .80 m-sec the amount of the early
rising part of curve, cut off would fill the space after the .80 m-sec peak and make a smooth
downward curve blending in with the backside of the little bump you got....So pour on the ball powder
and you can shoot cast fast, as they say,
because ball has that little extra shot
of burning power to minimize the slowing of the burn.I had looked at that trace for an hour before I figured what I had missed.
Hell to get old and slow.

AIU--If those spikes are MINI-SEE the powder
and wave speed is 5 to 10 times too fast to
propel bullets out of barrels. 5 to 10 times
too fast to add any speed to bullet. That type of super high powder burning speed, I think
locks up the bullet about as much as it propels the bullet ahead.And if too powerful barrel blows as bullet even though moving at say 2400 is still an obstruction to powder gases
traveling 15 times that fast..Ed Hubel

quote:

if your cases show no signs of pressure and there are no velocity increases when the MEGA spikes occur, then how can the spikes be measuring true internal pressure?

So when Sisk blew 3 barrels without damaging the cartridge case, that was caused by an electronic glitch?

If you welded the muzzle shut, would that increase the velocity?

I posted this on popenmann's site.--

"""Mtngun-Thought of something else.
Some more light has filtered into my brain.You call them mega spikes, but if they start as a Mini-SEE in the chamber area with cast bullets only, the breech sensor is seeing them, and a lot of their energy is soaked up expanding heavier breech section of the barrel, so as an effect, so
as to help minimize the effect on down the barrel at bullet base, and also that is reason that cutting barrel back on a Mini SEE that starts near chamber
doesn't make spike go away.

Ok now with light jacketed like Charley had, the Mini
SEE started little further down I think and cutting barrel made it go away.Have you seen any of his traces,with spikes?Ed.""

Folks think of what he has shown and what it means spikes still there with his particular
cast bullet situation that I described the mechanics of above, IE a Mini SEE starting in chamber area, and therefore SHORTENING BARREL
WON'T MAKE IT GO AWAY. And I think his barrel cutting has given a strong clue about where
and what is happening with his particular cast
loads. What I call a Mini-SEE or gun writers
or powder company folks, call a pressure excursion starting in chamber area..Does that seem too simple?..Ed

So perhaps the issue powder related. Might try two other ball powders, say H335 and BLc2. I'm thinking that these ball powders are less sensitive to the burn rate change we've been calling detonation.

We know that stick powders can detonate. I have theorized that stick powders may detonate from the high-pressure waved incident propagating back down the barrel. This wave is due to the cast bullet slowing abruptly.

Perhaps it is as simple as stick powders = spike[b] and [b]ball powders = no spike?

Popenman & mtgun are to be congratulated for suppling some real information.
So far as I understand it;
As you cut the barrel off the spike moves back.
If it is a pressure behind the bullet how does it know the barrel has been shortened ?.
If you hang a weight on the barrel the spike changes.
It's begining to look like it is a "vibration"
(toeque moment, doughnut wave, ect) in the barrel.
From past experience when you alter the free travel of the bullet the barrel vibrations will change ( the source of the sweet spot).
Great stuff!

A couple of things to bear in mind:

It's not a spike. It looks like a spike because the PT cannot graph the gage in compression. It starts out as a little, one cycle, damped sine wave, superimposed on the pressure decay, and grows as you increase charge. Since the PT cannot show compression, all you see is the positive part of the curve. It looks like a spike, but isn't.

It's not an electronic glitch. There is nothing in the PT smart enough to become confused. The signal chain is a simple analog differential amplifier, incapable of generating such a thing, and an 8 bit A/D converter, also incapable of generating such a thing.

It's not real chamber pressure, though it is a real, potentially destructive, event. A full charge of your favorite powder does not have sufficient energy to repressurize the chamber to even 60 KPSI with the bullet near the muzzle. Neither can any remaining part of a burned charge.

I think popenman's experiment, taping a gage to the barrel, is very clever. It nails the coffin shut on the "induced emf" sophistry.

quote:

damped sine wave

So there is a compression portion to the event? This is the first I have heard of this little bit of info...I assume that it is seen when using an o-scope directly, bypassing the commercial electronics?

Is it a single wave, or a rapidly building and decaying series?

quote:

So there is a compression portion to the event?

Yes. And I find it highly unlikely that the barrel somehow has a vacuum in it.

I have only seen this on the PT, and need to drag a scope to the range to get the full picture, and confirm it.

You can see it on the PT when the event is fairly small, so that the pressure decay curve provides enough positive bias to keep the whole event above zero. It is a single cycle, starting with the negative (compression) portion.

I'm having a hard time wrapping my mind around a (cumulative?) wave that can wreck a barrel.

Anyone have a hypothetical scenario? Dutch.

I haven't heard any theories, including my own, that really explain the data.

My least ridiculous theory is that it is a "doughnut" or "ring" wave that is caused by momentarily stretching and releasing the bore diameter. What causes the stretch? It almost behaves like a slight barrel obstruction... some kind of shock wave that the bullet penetrates, forcing compressed gas between the bullet and barrel, or some event that precipitates out water vapor, or... or... ???

quote:

Originally posted by Dutch:
I'm having a hard time wrapping my mind around a (cumulative?) wave that can wreck a barrel.

Anyone have a hypothetical scenario? Dutch.

Well I'm not going to support the "cumulative" wave idea.

When the bullet slows abruptly because the coefficient of friction changes, The change in movement becomes a change in pressure.

The change in pressue is a "wave front" that is now traveling down the barrel towards the breech. If you measure the pressure "in the wave", it is higher than the pressure ahead of the wave. Hope this makes sense.

The width of the wave is the round-trip travel time from bullet-base, to breech, back to bullet-base. The propagation velocity in a gas is dependant on the gas itself and it's temperature and I'm guessing 20us/inch @2000*F.

When powder burns, it is scattered down the length of the barrel. Although slow powders don't burn all bunched up in the cartridge, the gas produced moves faster than the "powder bodies", and therefore the bullet is ahead of the still burning powder.

All smokeless powders are progressive, i.e. they change to gas faster as pressure increases. Remember that pressure and temperature are directly poportional.

When the wave reaches some partially burned powder, the rate the powder turns to gas increases. If this rate is faster than the speed of sound at that temperature, it is called a detonation. In this case the detonation is a localized high-pressure spot. A detonation doesn't have to pressurize the entire barrel to be destructive - so you don't need much powder.

All powder, (black or smokeless), burns (changes to gas) at a rate determined by a flame front propagating over the surface area of the powder grain. If you raise the temperature(syn with pressure) fast enough, the burn is all at once and we have detonation.

I'm not sure why ball powders would be less sensitive to detonation. But I think it would be an easy test to see ball powders other than Winchester's exhibit the same characteristics.

quote:

Originally posted by denton:
I haven't heard any theories, including my own, that really explain the data.

My least ridiculous theory is that it is a "doughnut" or "ring" wave that is caused by momentarily stretching and releasing the bore diameter. What causes the stretch? It almost behaves like a slight barrel obstruction... some kind of shock wave that the bullet penetrates, forcing compressed gas between the bullet and barrel, or some event that precipitates out water vapor, or... or... ???

A longitudinal wave can be viewed as an event where the walls of the barrel are thickest at the positive peak of the wave and thinnest 180* later. Thin-thick-thin-thick, etc. all around the circumferance of the barrel. You could measure the effect my measuring the change in the length of the barrel - small, but measureable. The barrel is not bending, it is "breathing".

If you thicken or thin enough, i.e. high enough pressure, the metal will become plastic and the barrel will permanently deform, or with a little help from the pressure within, burst.

Alright, I'm buying the possibility of detonation of powder, sparked by a compression event. We know pressure isn't uniform down the barrel.

I'm having a HECK of a time buying the argument that the bullet slows down at any one point. There are two facts that pretty much allow us to exclude that event:

1) muzzle velocity is not changing. Bullets don't hop, skip or jump down the barrel. They gradually gain speed. A bullet can't stop, and still squirt out of the muzzle, 4 inches later, at the expected 2400 fps. Improbable to the point we can exclude it.

2) the inertia of the bullet is too high. A bullet is already traveling at 1,900 fps at 18 inches from the breech. We all know what a it takes to stop a bullet with that amount of energy: an inch of steel plate.

I think we can logically exclude the "bullet slowing down" hypothesis, with prejudice.

That doesn't mean that combustion doesn't get interrupted: it just means that the bullet doesn't act as an obstruction.

The facts are that a straingauge measures the deforming of the steel at the chamber consistent with a 100,000 PSI pressure reading, and one can blow the muzzle end off a rifle. A detonation of powder (which creates LOCAL pressure, but not uniform throughout the bore pressure), followed by that pressure event, through a shockwave, traveling towards the muzzle.

Problem is, the hacksaw event contradicts this! Shortening the barrel makes the spike occur sooner. I see no other explanation than that this has to be wave based.

That leads me to my original question. How can a wave event blow a muzzle off a rifle?

JMO, Dutch.

quote:

My least ridiculous theory is that it is a "doughnut" or "ring" wave

High speed photography can resolve how much distance? IOW, could the stretching be photographed, if it exists? Other non contact measurement methods exist too...but there is nothing like a photograph to 'prove' to the masses that something exists!

Here's a thought, don't know if the propogation velocities support it though:

-At ignition the powder rapidly (and normally) rises to a peak and falls off, initiating the primary wave...sorta like hitting a taut cable

-As the bullet travels, the wave propogates through the barrel steel, *ahead of the bullet* as the wave moves through the steel faster than the bullet travels down the barrel

-as the barrel thins, the wave amplifies

-as the wave hits the end of the barrel, it reflects back toward the muzzle

-as the bullet travels, a minor (secondary)expansion from the remaining pressure follows it

-as the primary wave and the secondary wave meet/cross, they amplify/resonate...with enough amplitude this *might* ring a barrel

-as the primary wave continues to the breech, it triggers the strain gauge again, but the short duration/high speed pulse skews the gauge into reading a much larger strain than the initial pressure

Blast away guys!

quote:

Originally posted by Dutch:
I'm having a HECK of a time buying the argument that the bullet slows down at any one point.

1) muzzle velocity is not changing. .

Changing from what? What is your reference?

Jacketed bullets, which have different guilding metal don't show the spike, but they don't go as fast per grain of powder. So how do we know that cast bullets have a uniform acceleration?

I don't think bullets have a uniform acceleration rate and when we say they slow down,it is not stopping, just a temporary
slowing of the rate of acceleration.
I will compare two types of loads causing
these spikes...

First his cast bullets.They are real tight at start, and makes quick initial peak, then once engraved jump faster than jacketed bullets of same weight as they are slippery, pressure drops too fast, powder burn slows, bullet slows,
pressure comes back building burning rate back up too high making another peak or what looks
like a spike.Because of initial tight bullet
the most heat and most mass of burning powder is near chamber and that is where the pressure
excursion or Mini-SEE starts, and starting there, cutting of barrel doesn't stop spike.

On Charley's light jacketed bullet loads.
On ignition they jump ahead faster
than the too slow of powder for that bullet weight, can keep up.. Pressure drops too fast,Powder burn slows, bullet slows, pressure comes back, powder burn picks back
up again, but the mass of burning powder is further ahead of chamber a little,
compared to example above,and when
Mini SEE or pressure excursion takes off.
It is closer to muzzle..
The initial easy to move bullet jumped and
a bigger part of powder mass moved forward.
Mini-SEE starts a little closer to muzzle, and that is why cutting off barrel helps to eliminate it for Charley.

That is the differences and how I think they work.We need more light bullet spike loads tested and barrels cut off to see what happens.

And because a Mini-SEE or pressure excursion travels many time faster than powder burning
speed before in the process, that it don't matter where Mini-SEE starts, the breech sensors wil see it as an instant happening.
The waves from Mini-SEE travel instantly compared to the regular burning mass of gases
and they travel through the regular burning
mass of gases, forcing the gases to bunch
up in a wave, ahead of wave fronm Mini-SEE.
That is why I think it doesn't take a lot of
extra powderand gases in a detonation mode to get the
space repressurized.And breech sensor to pick it up, or bunch up behind bullet and blow
barrel.

The reason I mention a part of the powder mass
moving ahead in last case, is that is how I
try to design my long straight big bore cases..IE get part of a large charge moved ahead
and burning further ahead, and along with amounts burnt in chamber gets more energy under the curve after the initial peak..Ed.

Ed, I'll buy that the rate of accelleration is not constant.

You just can't sell me that the bullet slows. No way, no how. Not with zero pressure on one side, and 10,000 PSI on the other, with too much inertia. The pressure inside that barrel may not increase consistently, but it's not going to go from 5,000 PSI to less than naught. Besides we have a Pressure Trace graph that is fairly smooth, and well above any range that would allow a bullet to slow.

Heck, even a 22LR bullet with 2 grains of powder behind it squirts out of the muzzle......

That's not too say that I disagree with the interrupted burn theory -- I think it is rather plausible that a powder plug is chasing the bullet and combusts.

We just have to translate that into a pressure event near the muzzle, that shockwaves into the chamber enough to give a 100KPSI reading..... FWIW, Dutch.

DLA, the muzzle velocity is not changing significantly from what one would expect. If the bullet stops, it basically has, what, 10" of barrel length left to achieve the same velocity as you would get from a 22" barrel?

Don't think so! JMO, Dutch.

Dutch--We are not talking about pressure dropping from 5000 to zero.But dropping too fast
from the initial peak of say 55-65000
psi.And you have to look at the downward side of the curve and compare say his cast bullets
to jacketed bullets and with same charge the curve is fatter for jacketed.. If that dropoff is too fast bullet will slow its acceleration rate a little, and it don't take much, and the system goes screwball.
That system is so tricky, and speed of acceleration, vs powder performance has to be perfect. That is why they make dozens of
different speeds of powder.It is a real sensitive process and moreso in necked cases.

As for a powder plug, not very much
on Mtngun's real tight cast bullets, maybe
some more on the light
jacketed of Charley's. And maybe reason cutting
barrel makes it go away.

I wonder what would mtngun's loads would do
if he swaged a couple down to bore size,
a regular fit like jacketed. Would they jump quicker like Charley's light bullets, and in
short barrel have no spike.A thought on something to check out.Ed.

quote:

A full charge of your favorite powder does not have sufficient energy to repressurize the chamber to even 60 KPSI with the bullet near the muzzle.

Good point, denton. This wasn't perfectly obvious to me, so I ran it through QuickLoad. I put 55 gn of powder in a chamber equal in volume to that of a .30-06 case plus about 20" of barrel and "fired" it under a 3 lb bullet -- kind of like running a bomb calorimeter. The pressure didn't even make 16 ksi.

OK, now I see why many here think this is some sort of strain wave moving down the barrel. Still, why does it not happen with some powders, even when the burning rates are about the same? If the initial pressure spike is about the same, how would the barrel tip "know" what type of powder caused it? Weird.

I am no professional ballistician, but it makes sense to me that if the pressure was real, especially 100k+, we would be seeing a difference in velocity. As well as I know from simple physics if you add that kind of pressure behind a bullet you will have a significant and measureable difference in velocity. I think the secondary spike issue is an electronic or vibrational abberation and not a true spike in pressure. Perhaps OK Shooter will chime in with some info. He has been doing these calculations longer than anyone I know.

quote:

Originally posted by D Hunter:
I am no professional ballistician, but it makes sense to me that if the pressure was real, especially 100k+, we would be seeing a difference in velocity. As well as I know from simple physics if you add that kind of pressure behind a bullet you will have a significant and measureable difference in velocity. I think the secondary spike issue is an electronic or vibrational abberation and not a true spike in pressure. Perhaps OK Shooter will chime in with some info. He has been doing these calculations longer than anyone I know.

Detonation is very locallized.

A grenade has a small amount of high-explosive. If you remove the fragmentation, the lethal distance is less than 6 feet. If you are holding it, it will shred you. If you are 30ft away it will annoy you.

Detonation only has to achieve a pressure above the yield strength of the steel to cause a ring and rings happen a lot.

quote:

Originally posted by Dutch:
Ed, I'll buy that the rate of accelleration is not constant.

You just can't sell me that the bullet slows. No way, no how. Not with zero pressure on one side, and 10,000 PSI on the other, with too much inertia.

Have you ever had a bearing seize? A rather abrupt change takes place. I'm postulating that something similar to seizing is taking place as the lead bullet slides down the bore.

One of the truisms from the experiments is that this secondary spike only occurrs with cast bullets, not jacketed bullets. And only when cast bullets are being driven to around 2500fps, not at the leisurely rate I run my 45-70

copper melts at 1980*F. Pure lead melts at 625*F.

D Hunter--They are not getting pressure behind the bullet in the normal sense of the word to
be able to push bullet. I think they are getting small detonation wave, that is so fast
that it doesn't have positive effect.
As I said it may bind the bullet as much as push it. The pressure from Explosives when they detonated travel in super fast waves, not a sustained buildup or push.Whatever is the event, it is giving physical signs like ringed and blown up barrels.Electrical couldn't do that.

ASDF- Yes what powder left may not repressurize
a long barrel section by itself if started from zero, up to initial pressure..But it is starting when pressure is about halfway back down on the curve like 25k, and
if a detonation type event, a third of powder and gases will send out a wave into the rest
of burning mass, bunching it and you have your
barrel section pressurized, or a sharp fast high pressure wave. High explosives have fast traveling waves.It don't stay pressurized very long, just a sharp, fast, blast and due to bullet already moving it drops fast, unless too high blowing muzzle. But still even that protects rest of the gun and shooter.Powder and gases in turbulent mix,
detonating have much more energy than if burnt
progressively.Your similation showed 16k and if detonated much more and if stuck in the middle of an already charged barrel at 25k, a spike or whatever it ends up being called, occurs.

dla-Also light jacket bullets with too slow of powder in certain cases. Don't know if it happens in big bore straight cases, Gonna have to find out for my peace of mind........Ed.

In all my experiments, I use only jacketed bullets. I see the spike effect quite often. It is not an effect limited to lead bullets. I think that the report of getting it with lead, and not with jacketed, applies only to one particular load, where lead bullets created the right conditions, and jacketed did not.

The detonation theory has one serious problem: The so-called spike starts out as a little sine wave, with the negative half cycle first, meaning the gage has gone into compression. That doesn't fit the theory. You can't have a detonation that first de-pressurizes the barrel.

The only way I can think of to get that result is if the detonation causes a ring wave that reflects off the muzzle (which it will), which, IIRC, inverts the phase of the wave.

Sign me, "As confused as ever, but on a higher plane, and about more important things."

quote:

Originally posted by D Hunter:
if the pressure was real, especially 100k+, we would be seeing a difference in velocity.

Velocity correlates to the area under the pressure curve assuming that there is minimal pressure on the nose of the bullet. If, for the sake of argument, you have significant pressure pushing on the nose of the bullet, then the math changes so that acceleration and velocity will correlate to the net pressure. For example, if there is 100,000 psi pushing on the base, and 90,000 psi on the nose, then the net pressure on the bullet is 10,000 psi, and the velocity will correlate to the 10,000 psi net pressure, not the 100,000 psi seen by Pressure Trace.

Is that the case with our secondary spike? No one knows. One of many, many theories is that the air being pushed ahead of the bullet forms a supersonic shock wave, and when this wave hits the muzzle, part of it reflects and heads back down the barrel until it collides with the bullet. Is this really what happens??? Vaughn's book has a shadowgraph of a shock wave emerging from the barrel while the bullet is still 3" from the muzzle -- about where our spike occurs. Hmmmmm. Does part of this wave reflect back into the barrel? If it did reflect, would it have a significant effect on our bullet??? How would you prove or measure such a thing??? I don't know. A reflected shock wave traveling inside the barrel would not necessarily create a radial strain that would be detected by a strain gage.

I vaguely recall from my gas dynamics class that there is such a thing as a reflected supersonic shock wave (in gas flow, not in steel like you guys keep saying), and that supersonic waves traveling down an open tube will either reflect back at the opening, or else diffuse into weak expansion waves, and that reflected shock waves can have a high pressure gradient, but there is generally no easy way to predict or quantify them, except to say that they can exist.

The bullets that blew off Charlie's muzzles were jacketed, not cast. The few cast bullets that I have recovered down range obviously did not melt.

As Denton said, no one theory seems to explain all the data. If powder is "catching up" to the bullet base, then shouldn't the spike go away if you hacksaw back to the "catch-up" point? If the bullet nose is colliding with a wave reflected off the muzzle, then why doesn't it happen with WW748 and WW760? And why cast bullets but not Barnes X?

I've been making inquires into the yield strength of barrel steel. Shilen (two of the Sisk barrels were Shilen) says "We use a special blend of 4140 and 416. Yield is 120-140 KSI on both." That sounds a little optimistic to me, but I'll have to take their word for it until I get my hands on a Rockwell hardness tester. Lilja says their barrels are 25 Rc, which would make them 100 - 115 ksi yield. It seems that most barrel makers stress relieve the barrels at around 600°C which tempers the metal down to 25 - 30 Rc and 100 - 120 ksi yield.

A simple experiment to distinguish between "air" shock waves and "steel" shockwaves would be to go to Sportsman's Warehouse and pick up a Limb Saver "barrel de-resonator" for $15.

This little gizmo should dampen the steel harmonics enough to greatly effect the observed pressure spike. If the effect is a harmonic of the steel.

If it is the effect of two gas shock waves superimposing, one from combustion, one from reflection from the muzzle, the de-resonator should have no effect.

The hacksaw experiment, in my mind, leaves no other possible conclusion that this is a wave/vibration/harmonic event. Nothing else can pass a prima facie investigation. Let's sort out if it is gas or steel waves.

And let's keep thinking on how a wave super-imposition at the bullet location translates into a pressure reading at the chamber? FWIW, Dutch.

Two hacksaw jobs had opposite results.
Cast didn't change with shortening barrel,
but light jacketed did.These two facts support my theory
explained above.And again---

Heavy cast bullet Mini-SEE or pressure excursion starts
close to chamber and cutting off barrel doesn't get rid of
it and the spike.

Ultra light jacketed bullet the Mini-SEE or pressure excursion
starts part way down barrel and cutting off barrel gets
rid of it and spike.

In both cases muzzle sensor picks it up and the one down the barrel is so fast relative to the regular happenings in a normal powder burn that it gets back to sensor instantly.
I think pressure waves are in the gases.Ed.

quote:

Originally posted by hubel458:
Two hacksaw jobs had opposite results.
Cast didn't change with shortening barrel,
but light jacketed did.These two facts support my theory
explained above.And again---

Heavy cast bullet Mini-SEE or pressure excursion starts
close to chamber and cutting off barrel doesn't get rid of
it and the spike.

Ultra light jacketed bullet the Mini-SEE or pressure excursion
starts part way down barrel and cutting off barrel gets
rid of it and spike.

In both cases muzzle sensor picks it up and the one down the barrel is so fast relative to the regular happenings in a normal powder burn that it gets back to sensor instantly.
I think pressure waves are in the gases.Ed.

Some wave propagation velocities:

• 2000*F gas = 20us/inch
  
• longitudinal wave in steel = 4.2us/inch
  
• transverse wave in steel = 8us/inch
  

Denton; The negative wave at the onset of the "spike" sounds a lot like a recoil moment in the barrel. If you put the gage on the other side of the barrel you will get a different reading. Once again not a pressure effect.
Good luck!

Hawkins-I wonder how big the negative wave will be when he checks.Could the neg wave be a wave front traveling away from sensor across the gases in the starting of mini detonation, which then sends back the big wave?
As some of us are theorizing that the cause of these is too fast of pressure drop, so could
this negative aspect be the extreme drop
showing up. Oehler's machines are set to stop taking readings if pressure drops to fast,
the MOST interesting aspect of manufacturers
actions about these events.I agree with Denton that it is not real chamber pressure as I
think it is a sharp, fast, pressure wave, of just enough duration to get a reading, on breech end or if damage occurs ring barrel near muzzle(or blow barrel).Ed

hawkins...

That's an interesting idea.

I thought about it for a few minutes, and I don't think it matches the data, though. The timing is wrong, and the gage is not positioned so it could "see" that moment.

BUT... if we keep picking at it, we will find an explanation that accounts for all the data. There are some sharp minds on this board.

Dumb question, but I've been assuming all along that these spikes are occurring while the bullet is still in the barrel. Is that true?

I just found this thread and it is very interesting. I have a question. Does the double peak ever occur in a barrel with the first round fired through a clean barrel? If not, could it be possible that the bullet scoops up the unburnt powder in the barrel and and compresses it to the point that it could detonate? Where could I see the pressure traces and pictures of the damaged barrels?

Good Hunting... from Varmint Al

Denton; If the gage is on the top of the barrel recoil will push the receiver back and up. This bends the barrel down. That lengthwise stress in the barrel will compress the gage due to poissons ratio (about 0.3). The way to measure hoop stress without getting a moment error would be to use two gages (top and bottom). They would have to be places in the circuit such that they would add (diagonally oposite legs of the bridge.
Vaughns "Rifle Accuracy Facts" shows bridge connections, and a moment measurement that looks a lot like the "spikes".
Good Luck!